D idom for removing array elements

[cym13 via Digitalmars-d-learn]

On Monday, 30 January 2017 at 08:50:14 UTC, albert-j wrote:
> On Monday, 30 January 2017 at 00:17:51 UTC, ag0aep6g wrote:
>
>> Removing works by overwriting the array with only the wanted 
>> values and discarding the rest.
>
> But then why do I get this:
>
>     import std.stdio, std.algorithm, std.array;
>
>     int[] arr;
>     foreach (i; 0..10) arr ~= i; // [0, 1, 2, 3, 4, 5, 6, 7, 8, 
> 9]
>
>     writeln("&arr[0]:", &arr[0]); // prints "7F56FAE93000"
>
>     arr = arr.remove!(x => x > 5).array;
>
>     writeln("&arr[0]:", &arr[0]); // prints "7F56FAE92020"
>
>     writeln("arr:",arr); // prints: "[0, 1, 2, 3, 4, 5]"
>
>
> It looks like arr.remove allocates new memory and copies the 
> data there.

No, remove works in-place, you are the one specifically asking 
for a reallocation here: instead of

arr = arr.remove!(x => x>5).array;

write

arr.remove!(x => x>5);


Complete example:

import std.stdio;
import std.format;
import std.algorithm;

void main(string[] args) {
     int [] arr = [0, 1, 2, 3, 4, 5];

     auto before = arr.ptr;
     arr.remove!(x => x>5);
     auto after  = arr.ptr;

     assert(before == after, "%s %s".format(before, after));
}